Comparison of Landsat 8 and Landsat 7 for regional measurements of CDOM and water clarity in lakes

For water clarity measured as Secchi depth (SD), we compared September 1, 2008 Landsat 7 and August 22, 2013 Landsat 8 images from path 28 using stepwise regression to identify the best model using all bands and band ratios including the new blue and narrower NIR band. The best water clarity model for Landsat 8 used the OLI 2/4 band ratio plus OLI band 1 and was nearly identical with a model using the OLI 2/4 band ratio plus OLI band 2. The latter model is similar to the model used for previous Landsat water clarity assessments, which used the ETM + 1/3 band ratio plus ETM + band 1. For SD measurements we found strong relationships with both sensors, with only slight improvements for the OLI sensor for the lakes in our datasets. In contrast to some previous reports that indicated Landsat 7's ETM + lacked sufficient sensitivity for reliable retrieval of CDOM, we found that overall both sensors worked well for water clarity and CDOM measurements. This will allow their continued use for current and historical measurements of important water characteristics on a regional scale.